The present invention relates to electric typewriter control systems and more particularly to a digital control system for controlling the actuation of individual type elements in an electric typewriter.
In the prior art, there are many devices for controlling the printing of characters in electric typewriters.
For example, the apparatus described in U.S. Pat. No. 3,658,161 shows how a code bail typewriter may be automatically and digitally controlled by the use of an electromagnetic actuation system. The system of the patent does not deal with individual key levers for each character but rather with code bails which must be operated in predetermined combinations to cause a particular character to be printed. Further, the system of the patent requires a synchronous operation and uses the existing motor rather an asynchronous system which employs a separate motor. Further, the system of the present requires that the electromagnet operate levers that transmit the operating power. This requires that the individual levers be large and bulky and would not be adaptable to an electric typewriter having individual key levers for each character to be printed.
Another patent which shows a control system for controlling an electric typewriter is U.S. Pat. No. 2,687,199 which shows apparatus for controlling individual key levers on a standard electric typewriter. The electromagnetic devices actually supply power and are large and bulky and are not economical or practical in that the center to center spacing of the magnets may not permit use of the system with a row of 44 key levers.
U.S. Pat. No. 3,294,117 shows an encoding system which reduces the number of solenoids or electromagnets required.
U.S. Pat. No. 3,372,788, shows a system for controlling the functional operations of an electric typewriter such as carriage return, back space, etc.
U.S. Pat. No. 3,420,351, shows apparatus for attaching and detaching a mechanism to operate an electric typewriter from a remote location. The primary thrust of this patent appears to be an approach to coupling the remote actuation device to the key lever.
U.S. Pat. No. 3,452,852 shows an electromagnetic system for controlling the actuation of key levers by a system which is mounted above the key levers and wherein the electromagnet supplies the power for the key lever actuation.
U.S. Pat. No. 3,502,187 shows the use of electromagnets to latch a bar which operates a key stroke. The patent appears to consider a system which is integral to the typewriter and not an accessory, attachment or add on device.
Each of the teachings in the patents briefly discussed above has certain disadvantages either in complexity of the mechanism, the cost of the apparatus, or in limitation of function or versatility.
Some of the patents show apparatus which only operate code bail type typewriter mechansims such as the "IBM Selectric". Others of the patents show apparatus unduely complex and costly.
Still other patents in this field show systems which prohibit the typewriter from being used in its intended mode as a manual typewriter in addition to use as a remote print out device.